This invention relates to a reinforcing material to be incorporated into a hydraulic substance such as cement, mortar, concrete, gypsum or clay, and a method for producing it.
Heretofore, it has been proposed to incorporate into a cement material a reinforcing material such as steel fiber, glass fiber, polypropylene fiber or split yarn to improve the physical properties, such as tensile strength, bending strength, impact strength and cracking strength, of the cement material.
However, in each of the fiber materials mentioned above, fibers are entangled rather strongly each other so that they are hardly dispersible in concrete material, and accordingly the distribution of fibers in the concrete material tends to be uneven. Further, such fibers, especially the steel fibers and glass fibers, require an employment of a special fiber beater or mixer such as a fiber dispenser, Omni mixer (registered trade mark) or auger mixer. Further, the steel fibers have a poor anti-corrosive property and are readily corroded by a salt content in the sea sands. The glass fibers tend to thicken as their viscosity increases upon admixing and are thus likely to form an undesirable fiber ball even when they are fed after disentangling, and they are inferior in the cement alkali resistance property.
Further, conventional polypropylene fibers have a circular cross section and a smooth surface and therefore they are likely to be slipped out when a bending stress is exerted on the concrete material containing them, and the concrete material is likely to be cracked or destructed, and therefore do not provide sufficient reinforcement.
Further, the split yarns of a synthetic resin are fibers of a net like structure which suggests a good physical bondage of the fibers with the concrete material. However, actually they do not provide satisfactory reinforcement as they are mixed in a bent form in the concrete material. Further, the split yarns themselves are bulky and it is difficult to disperse uniformly in the cement material.